PHY 1 QUIZ

Ecliptic

The apparent path of the Sun across the sky over the course of a year; represents the plane of Earth’s orbit around the Sun. The Moon and planets stay close to it.

Earth’s Tilt (23.5°)

Earth’s axis is tilted 23.5°, which causes the seasons and changes where the Sun appears in the sky throughout the year.

Ecliptic & Celestial Equator Relationship→

The ecliptic is tilted 23.5° above and below the celestial equator because of Earth’s axial tilt. This causes solstices and equinoxes.

Celestial Equator→

Earth’s equator projected into space; divides the sky into northern and southern hemispheres.

North Celestial Pole (NCP)→

The point in the sky Earth’s rotation axis points toward; located near Polaris.

Relationship Between North Celestial Pole & Celestial Equator→

The celestial equator is always 90° away from the North Celestial Pole, just like on Earth.

Altitude→

The angle of an object above the horizon.

Latitude→

Your position north or south of Earth’s equator.

Altitude–Latitude–North Celestial Pole Relationship→

The altitude of the North Celestial Pole is equal to the observer’s latitude.

Local (Solar) Time→

Time based on the Sun’s position in the sky; noon occurs when the Sun is highest.

Standard Time→

Time kept by time zones for societal convenience, not based on the Sun’s exact position.

Importance of Local Time vs Standard Time→

Astronomy relies on local time, because the sky depends on the Sun and Earth’s rotation, not clock time.

Sidereal Time→

Time measured by Earth’s rotation relative to the stars rather than the Sun; tells which stars are overhead.

Sidereal Time & Local Time Relationship→

Sidereal time is always local, because it depends on your location on Earth.

Precession→

A slow wobble of Earth’s rotation axis (~26,000 years) that changes star positions and celestial coordinates over time.

Impact of Precession on Star Coordinates→

Star coordinates slowly change, and the North Star will not always be Polaris.

Constellations (Scientific Definition)→

Officially defined regions of the sky used as a coordinate and mapping system.

Constellations (Cultural Meaning)→

Patterns used by cultures for storytelling, identity, timekeeping, and navigation.

Reading a Sky Map→

Requires knowing location, date, and time; maps are models that change depending on when and where you observe.

Archaeoastronomy→

The study of how ancient cultures understood and used the sky, using archaeological and cultural evidence.

Pleiades (Archaeoastronomy Example)→

A star cluster used across cultures for agricultural timing, mythology, and seasonal markers.

Chaco Canyon (Archaeoastronomy Example)→

A ceremonial center with solar alignments showing the integration of astronomy with agriculture and ritual life.

Zenith→

The point in the sky directly overhead an observer (90° altitude).

Meridian→

An imaginary line in the sky that runs from north to zenith to south; objects crossing the meridian are at their highest point in the sky.

Celestial Equator→

Earth’s equator projected onto the sky; divides the celestial sphere into northern and southern halves.

Ecliptic→

The apparent yearly path of the Sun across the sky; represents the plane of Earth’s orbit and is tilted 23.5° relative to the celestial equator.

Right Ascension (RA)→

The celestial equivalent of longitude; measures an object’s position eastward along the celestial equator, usually in hours.

Declination (Dec)→

The celestial equivalent of latitude; measures how far north or south of the celestial equator an object is, in degrees.

Mean Solar Time→

Time based on the average position of the Sun over the year; smooths out variations caused by Earth’s elliptical orbit and tilt.

Local Solar Time→

Time based on the actual position of the Sun in the sky at a specific location; solar noon occurs when the Sun crosses the meridian.

Standard Local Time→

Clock time used within a time zone; agreed upon for convenience and not tied exactly to the Sun’s position.

Sidereal Time→

Time measured by Earth’s rotation relative to the stars rather than the Sun; used to determine which stars are overhead.

Sidereal Time vs Solar Time→

Sidereal time tracks stars; solar time tracks the Sun. Sidereal time is about 4 minutes shorter per day.

Celestial Equator (on map)→

A curved line dividing the sky map into northern and southern halves.

Ecliptic (on map)→

A curved line tilted about 23.5° from the celestial equator; the Sun, Moon, and planets lie close to it.

Right Ascension (on map)→

Vertical or curved lines running north–south, labeled in hours.

Declination (on map)→

Horizontal or curved lines running east–west, labeled in degrees.

Constellation (on map)

A defined region of the sky with labeled stars, bounded by official borders.